Telephone system



R. D. CONWAY.

TELEPHONE SYSTEM.

APPLICATION FILED JUNE 6. 1918.

156,689., Patented Aug. 9,1921.

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"entree ears ROY I). CONWAY, OF CHATHAM, NEW JERSEY, ASSIGNOR TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. 1., A CORPORATION OF NEWYORK.

TELEPHONE SYSTEM.

neeacee.

Application filed June 6, 1918.

To all whom it may concern Be it known that I, ROY D. CONWAY, a citizenof the United States, residing at Chatham, in the county of Morris,State of New Jersey, have invented certain new and useful Improvementsin Telephone Systems, of which the following is a full, clear, concise,and exact description.

This invention relates to telephone exchange systems but moreparticularly to such systems of the central energy type as employservice observing means.

The principal object of this invention is the provision of improvedsignaling means for such systems.

In accordance with a feature of the invention a voltmeter relay isprovided which, when current flows through its winding in one direction,upon the connection of the cord circuit with the line circuit, will beenergized to cause the operation of other relays which will in turncause the illumination of a lamp at the service observing operators deskand which later, upon the disconnection of the cord circuit from theengaged line,.receives a current in the opposite direction to deenergizethe relays, thereby causing the effacement of the lamp.

For a more complete understandlng of the invention reference should behad to the following description taken in connect on with theaccompanying drawing, in whlch Figure 1 showsonly such portion ofatelephone system as is necessary for the proper understanding oftheinventlon; and Fig. 2 illustrates a second embodiment of the in-,vention.

Referring-now to Fig, 1, at A is .shown a subscribers station whoseline. B terminates at a central office at which a cord circuit C islocated for the purpose of extending the telephone lineB- Associatedwiththe line B is the usualline relay 4 which controls the actuation of theline signal 5. A cutofi relay 6 of the ordinary type is also providedfor severing the energizing circuit of line relay 4:. A voltmeter relay7 is shown-connected with the sleeve conductor of jack 8 for controllingthe operation of relays 10 and 11 and in turnthe service observing lamp12.

Assume that subscriber A initiates a call by removing the receiver fromthe switchhook, thereby causing the operation, of line Specification ofLetters latent.

Patented Aug. O, 1921.

Serial no. 238,495.

relay 4; to'establish a circuit for the line lamp 5, which is thereuponilluminated. The operator, upon observing the lighted condition of thislamp, inserts the answering plug 9 of the cord circuit G into the linejack 8, thereby causing the operation of cutoff relay 6 which opens theenergizing circu t for line relay 4 for causing the extinguishment ofthe line lamp 5. Since the contacts of the switchhook at station A areclosed, supervisory relay 13 operates to short-circuit the supervisorylamp 522 which is prevented from being illuminated. A circuit includingthe winding of the voltmeter relay 7 is also established upon theinsertion of the plug into the line jack, extending from battery throughthe alternate contact of supervisory relay 13, sleeve contacts of plug 9and jack 8, winding of relay 7 and resistance 14, to ground. The currentflow ing through the winding thereof is in such a direction, and .thepermanent magnet thereof is so poled, thatthe contact arm of relay 7 iscaused to'swing into engagement with contact 16, thereby establishing acircuit for relay 10 extending from. battery through resistance 18,contact 16 and winding of relay 10, to ground. The operation of relay.10 completes an energizing circuit for relay 11 extending from battery,through the winding of relay 11 and contactof relay 10 to ground- Relay11 on being energized accomplishes two results, first, the establishmentof a circuit for the lamp 12, located at the service observing operatorsdesk, and second, establishes a locking circuit for relay 10 extendingfrom battery through resistance 18, the middlelalternate contact of therelay 11, winding of relay 1O to ground. The operation of theselast men-'lilOIlGd relays completes a circuit which in conjunction with the otherapparatus associated therewith, forms what is wellknown in theelectrical art .as a Wheatstone bridge with the winding of the voltmeterrelay 7 forming the bridged connection. The resistances of the severalbranches are so proportioned that the current flowing through thebridged connection is thereby reduced to zero, causing thedeenergization of voltmeter relay 7. The subscriber at A. in restoringthe receiver to the switchhook upon the completion of the conversation,causes the deenergization of relay 13 which shortdirection which isopposite to that of the inicircuits resistance 21. The short-circuitingof this resistance thereby causes the operation of supervisory lamp 22which serves as a disconnect signal. The resistance of the supervisorylamp 22 is approximately the same as resistance 21 so that the balanceof the bridge circuit, as previously described, is maintained eventhough resistance 21 is short-circuited.

The operator upon receiving the usual disconnect signal withdraws theplug from the jack 8 and in so doing, causes a current to flow throughthe winding of relay 7 in a tial energization thereof. This circuit maybe traced from batterythrough the left-hand contact of relay 11,resistance 15, winding of voltmeter relay 7 and cutoff relay 6 toground, thereby repelling the armature so as to engage contact 17 whichin turn short-circuits the winding of relay 10 which releases to restoreall of the apparatus associated there'- with to normal.

Referring now to Fig. 2, which shows in detail the respective branchesof the circuit employed in connection with the service observing part ofthe system, the loop of four resistances which make up the Wheatstonebridge are represe'ntedby' the resistance R, which in Fig. 1 representsthe resistance 21, R representing the winding of cutoff relay 6, R and Rrepresenting the predetermined resistances 1A and 15, with Y the windingoftheyvoltmeter relay 7 forming th bridged connection which is usuallytermed the galvanometer branch of such an arrangement. The operator uponinserting a plug into alink jack closes the contacts 19 and 20 whicharerepresented by the sleeve contacts of the plugand jack, which causes acurrent to flow through the alternate contact 'of relay 13, resistance Rto the junction "point of the bridge, where it. divides, a portionflowing through the winding of "relay -7 and resistance R to ground, butthe larger "percentage thereof flowing through resistance R toground,causingan unbalanced condition to exist, which causes the displacementof the contact arm of the voltmeterrelay 7 "from its normal unactuatedposition into engagement with contact 16. Theen- The operation of relay,11 not only es-,

tablishes'a lockingcircuitfor relayf10 but also closes thecircuit forconnecting in circuit resistance R which forms the fourth branch of theWheatstone bridge. The resistance R is so proportioned that when it isconnected in circuit with the other branches the current flow throughthe winding of relay 7 is thereby reduced to zero, which allows thecontact arm thereof to be restored to normal.

v v e a second mentioned relay, gagement of thls contact establishesanen- When the operator removes the plug from the jack, contacts 19 and20 are opened so that a current is caused to flow from battery throughthe left-hand contactof relay 11 resistance R winding of relay 7 and resistance R to ground. A large portion of the current however, flowsthrough resistance R but due to the sensitiveness of the voltmeter relaythe amount flowing through the winding thereof is sufficient to cause adeflection of the contact arm. The flow of current through the windingof relay 7 is now in a direction which is opposite to-that previouslytraced. Contact arm of relay 7 is thereby deflected to engage withcontact 17 for short-circuiting the winding of relay 10, which isthereupon deenergizechto restore all other apparatus associatedtherewith to normal. I What is claimed is: l

1. A telephone exchange system comprising a telephone line, a cordcircuit'therefor,

a voltmeter relay energized upon the connection of the cord circu t Wlthtllfi l1ne,a

signaling device, a resistance, and means controlled by the energizationof the relay to operate the signaling device and to'connect saidresistance in circuit with the relay to the second relay to operate thesignaling device and to establish a locking circuit for the secondrelay. A

.3. A telephoneexchange s stem comprising a telephone line, a cordcircuit therefor,

a Wheatstone bridge comprising in two legs thereof cut-off relay and aresistance included in the cord circuit, and in the other legs thereoftwo predetermined resistances"; a relay, signal control means, a signalassociated therewith, and a second relay actuated upon the operation of.the first'meri tioned relay to. energize the signal control means and toformxa locking. circuit for the :4. A telephone exchange system icop'riing a telephoneline, a cord circuit therefor,

a lVheatstone bridge comprising-fin two legs thereof a cutoff relayandla resistance included in the'cord circuit, inith'e other I legs twopredeterminedresistances, a relay in the bridge; a signaling.device,andmeans controlled by the 'relay to operate the signaling device and toequalize 'thepotential at the terminals of the second mention ed relay.

. *5. A service observing system comprising 'a telephone line, a cordcircuit therefor, a

relay energized upon the connection of the cord circuit with thetelephone line, a predetermined resistance associated therewith, aservice observing signal, means controlled by the energization of therelay to actuate the signal and to connect said resistance in circuitwith the relay to thereby cause the release thereof.

6. A telephone exchange system comprising a telephone line, a cordcircuit, a Wheatstone bridge comprising in the branches thereof a cutoffrelay, a resistance included in the cord circuit, and two predeterminedresistances, a voltmeter relay in the bridge, an operating circuittherefor completed upon the connection of the cord circuit with theline, a service observing signal, and means operated upon theenergization of said voltmeter relay for causing the display of saidsignal and the equalization of the potential at the terminals of saidvoltmeter relay for effecting the release thereof, and a secondoperating circuit for said voltmeter relay established upon thedisconnection of the cord circuit from the line for again energizingsaid relay for causing the release of said means and the effacement ofsaid signal.

7. In a telephone exchange system in combination, a switch having anopen and a closed position, a source of current, a relay havingarwinding traversed by current of one polarity from said source upon theclosure of the switch and by current of an opposite polarity from saidsource upon the subsequent opening of the switch, and a signaling deviceenergized upon the operation of the relay by current of the one polarityand deenergized upon the subsequent operation of the relay by current ofthe opposite polarity.

8. A telephone exchange system comprising a telephone line terminatingin a jack, a link circuit terminating in a plug for extending the line,a signal, a relay, a normally ineffective operating circuit thereforrendered effective and completed through the contacts of the plug andjack upon the connection of the link circuit with the line to operatethe relay thereby causing the operation of said signal, and a secondnormally ineffective operating circuit for the relay independent of thecontacts of the plug and jack and rendered effective upon thedisconnection of the link circuit from the line for again operating therelay to effect the extinguishment of the signal.

9. A telephone exchange system comprising a telephone line, a linkcircuit for extending the line, a signal, a relay, a normallyineffective operating circuit therefor rendered effective upon theconnection of the link circuit with the line for causing theenergization of said relay, means operated upon the energization of saidrelay for causing the operation of said signal and the deenergization ofsaid relay, and a second normally ineffective operating circuit for saidrelay rendered effective by the disconnection of the link circuit fromthe line for again energizing said relay to effect the release of saidmeans and the extinguishment of said signal.

In witness whereof, I hereunto subscribe my name this 31st day of May,A. D. 1918.

' ROY D. CONWAY.

